1. Field of the Invention
The present invention relates to a crawler type traveling apparatus, a sprocket for a crawler belt and a segment thereof.
2. Description of Prior Art
A crawler type traveling apparatus is provided as a traveling apparatus (a chassis apparatus) of a crawler type vehicle such as a bulldozer or the like. The crawler type traveling apparatus is provided with an idler, a sprocket and a crawler belt which is wound around a periphery of the idler and the sprocket. The crawler belt is provided with a plurality of links 61 and a bearing structure body 62 connecting a plurality of links 61, as shown in FIG. 8.
As the bearing structure body 62, there is a structure provided with a pin 64, and a first and second bushes 65, 66 and 66 which are outward fitted to the pin 64. Further, there is set a state in which end portions 67 and 68 of the adjacent links 61 and 61 are overlapped, the second bushes 66 and 66 are press inserted into holes 67a and 67a of end portions 67 and 67 in an inner sides of the relatively facing links 61 and 61, and the pin 64 is rotatably inserted into the bushes 66 and 66. At this time, an end portion of the pin 64 is press inserted into holes 68a and 68a of end portions 68 and 68 in an outer side of the links 61 and 61. Further, a first bush 65 is outward fitted to the pin 64 between the end portions 67 and 67 in the inner side of the relatively facing links 61 and 61. Further, seal members 70 and 70 are interposed between the bushes 65 and 66, and a seal member 74 is also interposed between the second bush 66 and the link 61.
A pair of endless bodies 71 and 71 are formed by connecting the relatively facing links 61 and 61 respectively in a longitudinal direction via the pin 64 and the bushes 65, 66 and 66, and a shoe plate (not shown) is mounted to the endless bodies 71 and 71. Further, the constructed crawler belt is wound around a periphery of the idler and the sprocket, and travels in accordance with a rotation of the sprocket. In this case, as shown in FIG. 9, a gear tooth portion 73 of the sprocket 72 and the first bush 65 are engaged with each other.
In this case, in the conventional sprocket 72, a face width W of the gear tooth portion 73 is slightly smaller than a size between the inner end portions 67 and 67 of the links 61 and 61. Further, in the sprocket 72, a gear tooth side surface 75 facing to the inner end surface of the link 61 is formed in an unrelieved flat shape. Accordingly, when the gear tooth portion 73 of the sprocket 72 and the first bush 65 are engaged, an earth and sand makes an intrusion into a portion between a gear tooth bottom portion 76 and the first bush 65. Further, if the sprocket 72 becomes in a state of coming close to a side of any one of the link 61 or being in contact with any one of the link 61, the earth and sand has no escape, the earth and sand is pressed to a side of a seal member 70 in accordance with a pressing force of the sprocket 72 to the first bush 65, and there is a risk that an intrusion pressure of the earth and sand is applied to the seal member 70. If the intrusion pressure (a soil pressure) is applied, there is a risk that a seal function can not be sufficiently achieved in accordance that the earth and sand makes an intrusion into the seal member 70, and the seal member 70 is damaged (broken).
Further, if it is impossible to achieve the seal function, a lubricating oil supplied between the bush 65 and the pin 64 flows out to an external portion, the bush 65 and the pin 64 do not smoothly slide, and a seize is generated between the pin 64 and the bush 65, thereby reducing a service life of the crawler type traveling apparatus.